All issues / Volume 3 (2009) / Issue 6 (June)
This is an editorial article. It has no abstract.
Both Conducting and Ferromagnetic polyaniline containing nickel (abbreviated as PANI-Ni) is synthesized in a solution containing aniline, HCl and NiCl2, using peroxydisulphate as an oxidant and horseradish peroxidase as a catalyst. The conductivity of PANI-Ni is about 10–1 S cm–1. The result of electron paramagnetic resonance (EPR) spectra indicated that there were unpaired electrons in PANI-Ni, and the spin density of the PANI-Ni was 1.09•1019 spins g–1. The plot of magnetization (M) against the magnetic field (H) indicated that the PANI-Ni was soft ferromagnetic at about 300 K, the saturation magnetization (Ms) and the coercive force (Hc) of which were 4.5 emu g–1 (electromagnetic unit per gram) and about 55 Oe, respectively. UV-Visible (UV-vis) and Fourier Transform Infrared (FTIR) spectra showed that there was strong interaction between Ni2+ and PANI chains, but the backbone chains of PANI-Ni were hardly changed compared with PANI. Cyclic voltammogram results indicated that the PANI-Ni film was of excellent electrochemical activity.
A new class of organic-inorganic hybrid nanocomposites was obtained by blending PMMA-modified silsesquioxane hybrid materials with epoxy matrix followed by curing with methyl tetrahydrophthalic anhydride. The hybrid materials were obtained by sol-gel method through the hydrolysis and polycondensation of the silicon species of the hybrid precursor, 3-methacryloxypropyltrimethoxysilane (MPTS), simultaneously to the polymerization of the methacrylate (MMA) groups covalently bonded to the silicon atoms. The nanostructure of these materials was investigated by small angle X-ray scattering (SAXS) and correlated to their dynamic mechanical properties. The SAXS results revealed a hierarchical nanostructure consisting on two structural levels. The first level is related to the siloxane nanoparticles spatially correlated in the epoxy matrix, forming larger hybrid secondary aggregates. The dispersion of siloxane nanoparticles in epoxy matrix was favored by increasing the MMA content in the hybrid material. The presence of small amount of hybrid material affected significantly the dynamic mechanical properties of the epoxy networks.
Two novel tributyltin carboxylate maleimide monomers, tributyltin(maleimido)acetate and tributyltin(4-maleimido)benzoate, were synthesized by condensation reaction of maleimidoacetic acid or 4-maleimidobenzoic acid with bis(tributyltin) oxide. Copolymerization of these monomers with styrene was carried in dioxane at 70°C using asobisisobutyronitrile as free radical initiator. The structures of monomers and copolymers were confirmed by FT-IR (Fourier Transform Infrared), 1H and 13C NMR (nuclear magnetic resonance) spectroscopy and elemental analysis. The copolymers were characterized by solubility and thermal analysis.
The effects of iron powder as a synergistic agent on the flame retardancy of intumescent flame retardant polypropylene composites (IFR-PP) were studied. The thermogravimetric analysis (TGA) and cone calorimeter (CONE) were used to evaluate the synergistic effects of iron powder (Fe). The TGA data showed that Fe could enhance the thermal stability of the IFR-PP systems at high temperature and effectively increase the char residue formation. The CONE results revealed that Fe and IFR could clearly change the decomposition behavior of PP and form a char layer on the surface of the composites, consequently resulting in efficient reduction of the flammability parameters, such as heat release rate (HRR), mass loss (ML), Mass loss rate (MLR), total heat release (THR), carbon monoxide and so on. Thus, a suitable amount of Fe plays a synergistic effect in the flame retardancy of IFR composites.
Starch is a natural polymer which possesses many unique properties and some shortcoming simultaneously. Some synthetic polymers are biodegradable and can be tailor-made easily. Therefore, by combining the individual advantages of starch and synthetic polymers, starch-based completely biodegradable polymers (SCBP) are potential for applications in biomedical and environmental fields. Therefore it received great attention and was extensively investigated. In this paper, the structure and characteristics of starch and some synthetic degradable polymers are briefly introduced. Then, the recent progress about the preparation of SCBP via physical blending and chemical modification is reviewed and discussed. At last, some examples have been presented to elucidate that SCBP are promising materials for various applications and their development is a good solution for reducing the consumption of petroleum resources and environmental problem.
The flame retardancy of mono-component epoxy resin (RTM6), widely used for aerospace composites, treated with zinc borate (ZB), aluminium trihydroxide (ATH) and their mixtures at different concentrations have been investigated by morphological and thermal characterization. Cone calorimeter data reveal that combustion behaviour, heat release rate peak (PHRR) and heat release rate average (HRR Average) of RTM6 resin decrease substantially when synergistic effects of zinc borate and aluminium trihydroxide intervene. Thermogravimetric (TGA) results and analysis of the residue show that addition higher than 20% w/w of ZB, ATH, and their mixture greatly promotes RTM6 char formation acting as a barrier layer for the fire development. Depending upon the different used flame additives, SEM micrographs indicate that the morphology of residual char could vary from a compact amalgam-like structure, for the RTM6+ZB system, to a granular structure, characterized by very small particles of degraded resin and additive for the ATH.
Thermoplastics having various short and long-chain branches, characterized by the melt index measured at the processing temperature – according to their average molecular mass – can be processed using universal principles, independently of their chemical composition. The average molecular mass is the result of a molecular mass distribution, being the fingerprint of the chemical synthetic technology. The actual shape of the shear viscosity function aiming at the quantitative characterization of viscous flow, containing material-dependent parameters, depends on the ratio of high and low molecular mass fractions, the width of the molecular mass distribution function and on the number of short and long chain branches. This publication deals with the critical analysis of the mathematical methods of transforming these two curves of basic importance into each other.